Traffic control system



Aug. 28, 1956 H. A. WILCOX TRAFFIC CONTROL SYSTEM 2 Sheets-Sheet 2 FiledNov. 50, 1953 VFL VFR/

' FIGS.

FIG.4.

INVENTOR.

HARRY A. WILCOX ATTORNEY United States Patent 2,761,120 TRAFFIC CONTROLSYSTEM Harry A. Wilcox, Westport, tionm, assignor to Eastern Industries,Incorporated, East Norwalk, Colin, a corporation of Delaware Thisinvention relates to traffic control systems and a control apparatus fortr'afiic signals in such systems, and relates more particularly toelectrical apparatus for remote control of the total lengthof thetraflic signal cycle over a wide range, While retaining a substantiallyconstant length for apart of the cycle such 'as the trafric clearanceintervals, following the respective traffic g'o intervals in the signalcycle.

The invention further relates to an improved masterlocal control systemand apparatus for the control of one or more of a series of intersectiontraflic signals in which a master controller provides a variablefrequency power to the one or more local controllers to drive the localcontrollers at a faster or slower rate as desired, during one part ofthe local traffic signal control cycle, as during the green signalperiods for the respective intersecting streets controlled by thesignal, to thus control the length of the green period and total cycleremotely, but in which the local controller is operated on fixedfrequency power during another part of the cycle, as for example duringthe yellow signal periods ordinarily provided for traflic clearancefollowing the green period's, where it is desired to have this latterpart of the cycle of substantially constant length while varying thefirst mentioned part of the cycle over a wide range. h M

Various systems for coordinating the trafiic signals at a series ofintersections alohg a common street or highway are already well known,including systems by which a maser controller provides a' common cyclelength for a series of local signal controllers, and the localcontrollers may be individually adjusted to time the beginning or theend of the common street green signal period with respect to a commonreference point in the cycle usually referred to as the zero offsetpoint, and the local controllers can also be individually adjusted todetermine the relative lengths of the green signal periods for therespective streets and the following yellow signal periods, theproportioning of the green signal periods of the signal cycle beingusuallyrefe'rred to as the split" of the signal cycle.

Such proportioning of the local signal cycle is quite commonly done bymeans of a rotary dial unit on which pins or keys may be located indesired angular relation ship, the dial being rotated so that the pinsengage contacts to actuate a step-by-step rotary switch unit whoseseveral positions operate the desired green, red and yellow signals. Thelocal rotary dial unit is ordinarily resynchronized once per cycle withthe master controller cycle unit. y m

It is already also well-known to employlv arious means of lengtheningthe total cycle of the local controller by remote control from themaster controller. One of the most effective of such remote controlmeans has been the operation of a synchronous motor unit in the localcontroller from a variable frequency power supplied by the mastercontroller as disclosed in S. Patent 2,542,978, granted February 27,1951, to John L. Barker "ice for example. Such systems are most flexiblein providing a wide range of adjustment of the total time cycle, in

which the longest time cycle may be two or three or more times thelength of the shortest time cycle. Where said systems have such a Widerange of adjustment it has been found to be a disadvantage for certainparts of the signal time cycle, as for example the yellow clearancesignal periods, to be lengthened and shortened along with the totalcycle, as is the case where the variable frequency control is, applieddirectly to the local rotary dial unit for example. 1

Therefore, in accordance with one aspect of the present invention, meansis provided in connection with the local controller to provide theremotely controlled variable frequency power to drive the local rotarydial unit during one part of the cycle, as for example the greenperiods, and to apply a local fixed frequency power to drive the localrotary dial unit during another part of the cycle as for example duringthe yellow periods, thus permitting the total cycle to be widely variedalong with the green periods but to retain substantially constant yellowperiods.

1 In accordance with a further aspect of the invention the mastercontroller is provided with a total cycle determining unit which isdriven from the common variable frequency power over the major part ofits cycle but is driven by a substantially constant frequency powercorresponding substantially with the local fixed frequency power duringanother part of its cycle to provide a total cycle for itsresynchronization unit comparable to the total cycle of the localcontrollers, the resynchronization unit assuring that the localcontrollers will be restarted in synchronism once per cycle for example,and the master control cycle unit having a slightly longericycle thanthe local controllers over the entire range of adjustment.

It is a general object of the invention to provide an improved trafliccontrol system for varying by remote control over a wide range thelength of the total cycle of one or more traflicsignals whilemaintaining apart of such cycle. substantially constant.

It is a more specific object of the invention to provide an improvedtraflic control system in which the relative proportion of therespective green signal periods forthe intersecting roads at individualtrafiic signals is locally determined by individual controllers and. inwhich the total signal cycle of such controllers is varied from a. com;

mon master controller While maintaining substantially constant theindividuahproportioning of the green or go periods, and in which theyellow or clearance periods ,are a nt in d at a sub al ons ant v l 9Y awid range of adjustment of the total cycle by such remote control fromthe mastereontroller j i It is a further object of the invention toprovide proved means for operating a local traflic signal corn trollerthrough a variable total time cycle and variable length of greener goperiods While maintaining substantially constant yellow or clearanceperiods and a substan-- tially constant ratio between the respectivegreen or go peiifodsof the signal cycle. I p

is so an bje of e in e n t r de a traf ic control system in which oneormor e individual traiiic controllers are operated at varying timerates to control the total cycle length over a wide range by variablefrequency IlljlVlllgjPQWfll supplied to the local controllers from asingle master controller, and in which means are provided in connectionWith the local controller to make such variable frequency driving powerineffective on the local controller during a part of the signal cycleproviding the yellow or the clearance signal periods for example andsupplanting such variable frequency power by a substantially fixedfrequency local power drive during such yellow or clearance periods.

It is a still further object of the invention to provide a master-localcontrol system for traflic signals employing variable frequency powerfor the local controllers supplied by the master controller for varyingthe total signal control cycle and employing means at the localcontroller for supplanting the variable frequency power drive at thelocal controller during the yellow or clearance signal parts of thecycle to provide a substantially constant period for such parts of thecycle, and means at the master controller for operating a master cycleresynchronization unit from the variable frequency power during one partof its cycle and from a fixed frequency drive during another part of itscycle, with the latter part of its cycle corresponding to the timelength of the local yellow or clear-- ance periods approximately, saidresynchronization unit serving to resynchronize the local controllerwith the master controller.

Other objects of the invention will appear from the accompanying claimsand from the following description with respect to the drawings inwhich:

Fig. 1 illustrates in schematic form the master control apparatus for atraffic control system according to one embodiment of the invention, andproviding output master control lines for control of local signalcontrollers.

Fig. 2 similarly illustrates a set of trafiic signals and associatedlocal control apparatus in schematic form for one intersection, and inblock diagram form for a second intersection along a highway or roadway,and the connections with the master control apparatus of Fig. l for atrafiio control system.

Fig. 3 illustrates in schematic form the local signal control apparatusfor conection to the master control lines according to anotherembodiment of the invention, in which relays are employed for therespective individual green signal circuits for control of theconnection and disconnection of the master variable frequency power andlocal fixed frequency power for operation of the local controller. I

Fig. 4 illustrates a schematic diagram of the local control apparatus asin Fig. 3 but according to another embodiment of the invention in whicha relay is controlled by or operated in both of the yellow signalperiods to control the connection and disconnection of master variablefrequency power and local fixed frequency power for the localcontroller.

Fig. 5 illustrates a schematic diagram similar to Fig. 4 but accordingto another embodiment of the invention in which a relay controlled by oroperated during both green signal periods serves to connect anddisconnect master variable frequency power and local fixed frequencypower for the local controller.

Fig. 6 illustrates still another chematic diagram in which directcircuits from cam operated contacts for Referring now to Fig. 1 in moredetail the master control apparatus is illustrated as comprising twoprincipal components shown in the broken line blocks VFG and MCUrepresenting the variable frequency generator and the master cycle unitrespectively, together with the several output lines or circuits VFL andVFR representing the variable frequency line and return respectively,and RSL and RSR respresenting the resynchronization line and returnrespectively.

A schematic circuit of one form of variable frequency generator is shownin the lefthand broken line block designated VFG, employing a series A.C. motor designated MM and an associated A. C. generator driven by themotor MM. The speed of the motor MM and the generator GN is varied bymoving the top PV along the potentiometer PR. This variablepotentiometer thus provides an adjustable controlling resistance inseries with the motor circuit via the motor coil MM23, to vary 4 thespeed of the motor and consequently the frequency of the output of SNfrom the brushes 1ll2 and along the variable frequency lines VFL andVFR. The fixed resistance FR is preferably included in series with PRand the motor circuit as a protective minimum res-istancef Theadjustment of the potentiometer PV-PR may be made by moving the tap PVmanually or by means of a time clock or other timing device, or by meansof a trafiic actuated cycle selector or offset selector as in thc Patent2,542,978 referred to above, either smoothly or by steps to one ofseveral tap positions along the potentiometer PR, to vary the outputfrequency on the lines VFL and VFR.

It will be appreciated that while the motor-generator form of variablefrequency generation is illustrated for simplicity an electronicvariable frequency generator may be used if desired, such as thefamiliar audiofrequency generator employed in electric laboratories, inplace of the motor-generator type of variable frequency generator shown.

The master cycle unit MCU includes an amplifier MA operated from thevariable frequency line to repeat and amplify the variable frequencypower to drive the master synchronous motor MSM to rotate the cams MCYand MCR. The cam MCY controls the switch MSCMSK- MSV to connect themotor MSM between variable frequency and fixed frequency power duringdifferent parts of the cycle, and the cam MGR controls the switch MSR toprovide a cyclic resynchronization pulse over the lines RSL and RSR.

The amplifier MA has its input side connected via wires 13 and 14 to thevariable frequency lines VFR and VFL respectively and has its outputrepresented by the Wires 15 and 16. The wire 15 thus connects one sideof the output of the amplifier to one terminal MSM3 of the operatingcoil of the motor MSM. The wire 16 on the other side of the output ofthe amplifier is connected to the switch contact MSV. The other side ofthe motor coil MSM2 is connected via wire 19 to the movable switchcontact MSC, and the other switch contact MSK is connected to a fixedfrequency power source indicated by the plus in a circle, which may forexample be ordinary 60 cycle alternating current power.

As the motor MSM rotates, the corresponding rotation of cam MCY willconnect the movable switch contact MSC to the contact MSK to apply thefixed frequency power to the motor coil MSM2 during a relatively smallpart of the total cycle of cam MCY. The cam and switch contacts areshown in Fig. l in this position, in which the contact MSV is separatedfrom contact MSC to discon nect the motor MSM from the amplifier MAoutput at wire 16.

As indicated in Fig. 1 these circuits are maintained in this positionfor only a small part of the cycle corresponding approximately to thetime of two yellow signal periods of the order of about 6 seconds totalfor example in one preferred embodiment of the invention. However,during the remainder of the cycle of cam MCY the movable contact MSCwill be disconnected from contact MSK and connected to contact MSV, thusconnecting the motor coil at MSM2 via MSV-MSC to the amplifier outputline 16, to operate the motor MSM from the variable frequency poweroutput of the amplifier repeating in amplified power form the frequencyfrom the lines VFL and VFR, the motor MSM operating fast or slow inaccordance with the frequency of the applied power. The cam MCRpreferably closes the contacts MSR throughout all but avery small partof the total cycle. and opens the contacts MSR during this small part ofthe cycle, for example one or two seconds in length, so that power fromone side of the power supply line indicated by the plus in a circle isconnected to the resynchronization output line RSL during most of thecycle but is disconnected momentarily once per cycle for example. Thereturn resynchronization line RSR is illustrated as connected to theoppositeside' of thepower supply as indicated by ther'ninus sign 'in acircle, whioh' also may be grounded as shown for example.

Referring now to Fig. 2 illustrating one form of'local control apparatusand associated traffic signal, the lines extending across the lower'part of'this Fig. 2 and designated VFL, VFR, RSL, RSR are extensions ofthe correspondingly designated output lines to the rightdf Fig. 1, sothat if the left side of Fig. 2 is connec'tedtothe right side of Fig. 1a Complete master localcdhtrol system is illustrated. These mastercontrol lines at the bottomof Fig. 2 can beconsi'deredas extending alonga highway or roadway for example common to several intersections havingindividual l-ocal control units and associated traffic signals. Onelocal control unit, and includingo'ne set of ttaific'signals S for oneatlic intersection, is illustrated schematically within the broken litrebloc'kdesignated LOU-1, and is shown connected to the master controllines way 'of the wires 21, 22, 23, and 2 A similar but smaller brokenline biock'desigriated. LCUZ represents a second local control unit fora second intersection along the common roadway or highway, and includingits traffic control signals, this second "unit 'LCU2 being similarlyconnected to the several master control lines as indicated.

' It will be appreciated that the general construction of thelocalcontrol units LCUI and LCUZ may be the same but these units maybeadjusted for aditlerent proportioningof the green signal periods for therespective streets or in other words a dilferent distribution of thesignal cycle for example as will be more fully explained below. Thelocal control units may also "be adjusted for different relation oftheir'respectiv'e signal cycles to theresynchronization point controlledby the master cam MCR of Fig. l as more fully explained below.

The signal S in the upper part of Fig. 2 illustrates schematically thetwo sets of signals for a common form of trafic right-of-way signal forintersecting streets A and B torexample (not shown), including thered,yellow and :green signals AR, AY and AG respectively for street A andthe red, yellow and green signals 1BR, BY and 'BG for street B. One sideof all of these signals is connected to one side of an ordinary powersupply as indicated by the minus sign in a circle, and the other side ofthe signals are connected respectively v by individual lines LAR, LAYand LAG and by lines LBR, L'BY and LBG to a local drum controllerrepresented. by the solid block LDC. This local drum controller any beone of several well known types of which the most coinrnon is a set ofcam operated switches an opening and closing the respective signalcircuits as the cams are retated by a motor drive which may preferablybe of the step=by-step type widely used in traffic signal controllers.One 'form of such step-bystep local drtim controller is illustrated inpart in Fig. 3 for example. i

The power supply for the local drum controller and associated otherapparatus is indicated schematically at the left of Fig. 2 with thepower side of the line indicated by a plus in a circle and the groundedside of the line indicated by minus in a circle for example, which mayrepresent an ordinary local 60 cycle alternating current power supplyfor example. The lead 20 at the lower side of the block LDC'indicates anactuating line for operating the drum controller {from one step to thenext in its cycle under the control of the local dial switch unit LDl-LDSE operated by the local synchronous motor unit LSM. The same localsynchronous motor LSM also drives the dial switch unit LDRLDS34indicated below it in Fig. 2, which serves to resynchroniae the localdial switch assembly with the master cycle unit once per cycle.

In the form illustrated the dial switch unit LDS3- i is normally closedthroughout most of the cyele of the rotary dial .LDR and associatedrotary dial LD1, but the switch LDS3-4 is opened by theresynchronization pin RP illustrated in the lower leftquadrant of medialLDR, the pin RP deflecting the movable contact LDS3 as the dial LDRrotates through its cycle. This momentaryinterruption of the contactsLDS34 opens the circuit of the motor coil LM2LM3 of the localsynchronous motor LSM via wire 27, thus stopping the motor LSM and itsassociated rotary dials LD1 and LDR until the resynchronizing releasepulse is received via relay LRS from the master resynchronizing linesRSLRSR from the master controller.

If as is normally the case the local rotary dial assembly issubstanti'allyin synchronism with'the master cycle unit MCU of Fig. 1then the'local rotary dial assembly will be stopped only momentarily atthis resynchronizing point since the cam MCR in the mastercontrol unitshown in Fig. 1 will then open the contacts MSR and thus cut olt powerfrom theresynchronization line RSL, thus releasing momentarily the relayLRS which is connected across the lines RSL and 'RSR via wires 22 and21. This momentary release of relay LRS causes its movable contact LRS3to fallback so as to close with contact LRS4 to provide a shunt circuitaround the open contact LDS3-LDS4, thus reclosing the circuit for themotorcoil LM2-LIVES to restart the motor LSM and the associated rotarydials in synchronism with the master'control unit.

As the local rotary dials then resume rotation the passage of the pin RPcauses the reclosure of the contacts EDSZ'si so that as the masterresynchronizingcontacts MSR are again closed by the continued rotationof h .ECR, and relay LRS is consequently again reenergized to reopen itscontacts LRS34, the dial control contacts 'LDS3--4 maintain the dialmotor circuit closed through the balance of the cycle. Although thecircuit includes contacts of relays REY and RAY, the operation of theresynchronizing circuit as described, above is not appreciably affectedby the position of either of these relays.

it .will be understood by those skilled in the art that braking meansmay be employed to stop the rotary dial motor LSM quickly so as to avoidcoasting throughthe resynchronization position, and it will be alsounderstood that the arrangement of the contacts LDS3-4 and LRS3-4 couldreadily be reversed so vthatthepin RP would close the dial switchcontacts LDS3A--4, to close a motor brake coil circuit to stop the motorin opposition to a normal continuously energized driving coil,-in whichcase the relay contacts corresponding to 'LRS3-4 would then be arrangedin series with LDS3-4 and the brake coil to be closed through most ofthe cycle. and opened only momentarily by the release of relayLRS toreopen the brake coil circuit to permit the rotary dial motor to proceedfrom the resynchronization position. In this latter alternativearrangement, the driving coil terminal LM2 would be directly connectedto wire 29 and thus to RBY6 for example. i

The rotary dial LD1 in Fig. 2 is provided with several pins DP spaced indesired angular relation around the rotary dial to close the contactsLDS'l momentarily several times during each revolution of the rotarydial so as to operate the step-by-step controller LDC one step at a timefor switching the signal circuits. These signal circuits are switched bythe, drum controller through successive positions to providothe greenandthe following yellowperiods for street A and then the green andfollowing yellows signal periods for street B and to provide a redsignal period for street olvefrlapping the A green and yellow periodsand to ,provide a red signal period for streetA overlapping the B greenand yellow periods respectively for example. i i

n win be appreciated that the dial LDl is sh wn its simplest form withfour pins DP to providethe basic four steps of the cyclecomp'rising thetwo green lsig nal periods and the two yellow signal periods but morpins could be provided in the rotary dial and more steps in the cycle ofthe drum controller so that each green signal period could overlap morethan one position for example, as is well known in the art.

The angular distribution of the pins DP around the rotary dialdetermines the distribution of the total cycle among the green periodsand yellow periods for any given constant speed of rotation of the dial,and determines the length of the green periods for any given setting ofthe frequency of the variable frequency power. Thus the pins DP may beset for a 60%40% split of the green periods at one local controller LCUland may be set for a 50%50% split at another local controller LCU2, andthese respective splits will be maintained at the respective controllerswith a short cycle and short green periods of the variable frequency isset at a relatively high level and with a longer cycle and longer greenperiods if the variable frequency is set at a relatively low level, forexample.

It will be appreciated that the starting point of the main street or Agreen signal for example in relation to the resynchronization point andthe other signal controllers along the main street can be determined bythe relative positions of the resynchronization pin RP and the pins DPdetermining the start of the main street or A green in cooperation withthe drum controller. The length of time that the rotary dial unittravels from the resynchronization point controlled by pin RP to thebeginning of the next following main street green is usually referred toas the offset for that controller or signal, and the pin RP isordinarily located in one or the other of the green signal parts of thecycle to avoid having the rotary dial unit dwell in a yellow positionuntil resynchronized if it should be out of step. The corresponding pinRP (not shown) in the other local controller unit LCUZ may be set thesame as the pin RP in the unit LCUl to maintain the two controller unitsin synchronism, or the pins RP in the respective controller units may beset in different relative positions to the pins DP controlling thebeginning of the main street or A green for example to maintain apredetermined desired phase relation between the controllers so that thebeginning of the green at one will lag behind the beginning of the greenat the other to allow for travel time along the main street between thecontrollers and associated signals for example.

The block indicating the drum controller LDC and its rotary dialassembly for operating and resynchronizing the drum controller as justdescribed are shown enclosed in a broken line block designated LC sincethese components may be identified conveniently as an ordinary localsignal controller for operating the signals S. However, outside of thebroken line block LC representing the ordinary local controller andwithin the outer broken line block LCUl representing one complete localcontrol unit, the relays RBY and RAY are added in accordance with oneembodiment of the invention to control the operation of the localsynchronous motor LSM of the rotary dial assembly to permit the rotarydial cycle to be lengthened or shortened, along with the respectivegreen periods for the respective streets A and B, by remote control fromthe master controller over the lines VFL and VFR, while keeping theyellow signal periods substantially constant.

This is accomplished in the embodiment of the invention illustrated inFig. 2 by interposing contacts of the relays RBY and RAY in the circuitsof the coil LM2 LM3 of the roary dial motor LSM, these relays beingoperated in the respective yellow signal periods of the controller toconnect the LM motor coil to local fixed frequency, such as for examplethe ordinary 6O cycle alternating current local power supply representedby the plus and the minus in circles. When neither of these relays RBYand RAY are operated, as for example in either of the green signalperiods of the signal cycle, the contacts of these relays connect themotor coil LM2LM3 via wires 25 and 26 to the output side of the localamplifier LA, the input side of which is connected via wires 23 and 24to the variable frequency lines VFLVFR to provide variable control ofthese green signal periods.

Considering these relays and their control circuits more specificallythe relay RBY has its coil connected between the yellow signal poweroutput wire LBY and the negative power terminal, and the relay RAY hasits coil connected between the yellow signal power output wire LAY andthe negative power terminal, the wires LAY and LBY serving to operatethe respective signals AY and BY when power is applied in the respectiveyellow sig* nal of the drum controller LDC. The coil of the relay RBYcontrols the movable contacts RBY3 and RBY6 and the coil of the relayRAY controls the movable contacts RAYS and RAYG. These movable contactsare shown in their normal rest positions with the relays deenergized inFig. 2.

With these relays RBY and RAY both deenergized as shown in Fig. 2, andalso assuming that the pin RP is in the position shown in Fig. 2, theLSM motor coil LM2 will be connected via wire 27, LDS3-4, wire 29,normally closed contacts RBY6RBYS, normally closed contacts RAY6--RAY 8,and wire 25 to the output of the amplifier LA, and the other terminalLM3 of the motor coil will be connected via Wire 28, the normally closedcontacts RBY3RBY5, the normally closed contacts RAY3-RAY5, and wire 26to the other side of the output of the local amplifier LA. This localamplifier is a form of repeater amplifier for repeating and amplifyingthe variable frequency from the master control lines VFL-VFR to operatethe local synchronous motor LSM of the rotary dial assembly.

It will be appreciated by those skilled in the art that although itwould be possible to drive the several local controllers directly fromvariable frequency power supplied by the master controller, this wouldinvolve the transmission over the variable frequency lines ofconsiderable amounts of current and would be inefficient from the viewpoint of the size of the wires required to avoid excessive line losses.Thus in the preferred embodiment of the invention the variable frequencypower supplied by the master controller on the lines VFL-VFR is ofrelatively low voltage and very small current, and the severalamplifiers MA and LA serve to repeat and amplify the low power variablefrequency to a substantial power variable frequency for operation of theseveral synchronous motors in the respective controllers. The output ofthe amplifiers is of suflicient voltage and current capacity to operatean ordinary small size synchronous motor of the type already familiar inrotary dial type traffic signal controllers, for example.

It is now assumed that the rotary dial assembly has rotated so that thelocal drum controller LDC is in the AY signal position. Power from LDCon wire LAY will operate the signal AY and also operate the relay RAY toopen its normally closed contacts RAY3RAY5 and RAY6-RAY8 and to closeits normally open contacts RAY3RAY4 and RAYd-RAYT Since the relay RBY isdeenergized at this time, the only change in the circuit from that justdescribed above, is that the motor terminal LM3 is now connected viawire 28 and RBY3RBY5 and RAY3RAY4 to the positive power terminal, andthe wire 29 controlling the other motor coil terminal LM2 is connectedvia RBY6RBY8 and RAY6-RAY7 to the negative power terminal, these powerterminals representing for example a fixed frequency local power supplysuch as 60 cycle alternating current.

Similarly if it is assumed that the rotary dial assembly is in anotherpart of its cycle to operate the B yellow signal BY, the relay RBY willbe operated from power on the line LBY which also operates the signalBY, and the relay contacts BY6 and RBY3 will be moved to interrupt thevariable frequency connection for the motor coil LM2-LM3 and to closethe fixed frequency connection signal circuits.

for this coil. These connections can be traced from the control wire 28or" the coil terminal LM3 via the now closed contacts RBY3-RBY 4 topositive power, and from the wire 29 controlling the coil terminal LMZas above described via the new closed contacts RBY6-RBY7 to the negativepower terminal. It will be noted that in the respective yellow signalperiods the operation of the respective relays RA Y and RBY interruptsthe connection of the variable frequency power output of amplifier LA,by opening the contacts RAYS-RAYS and RAY6-RAY8 in the case of the relayRAY, and by the opening of the contacts RBYS-RBYS and RBY6RBY8 in thecase of relay RBY.

Reviewing briefly the operation of the local controller under control ofthe master controller the local synchronous motor LSM, which controlsthe local signal cycle through theassociated rotary dial assembly and inturn through the local drum controller, is operated through the A greenperiod and B green period of the local controller from the variablefrequency power from the master control so that these two green signalperiods can be shortenedor lengthened remotely from the master control,and this local synchronous motor LSM is operated from local fixedfrequency power during the two yellow signal periods so that theseperiods may remain constant despite the wide variation in the cycle ofthe rotary dial as controlled by the master control.

The master control motor MSM is designed to beslightly slower than thelocal control motor LSM and thus to have the master controller completeits cycle on a slightly longer time period than the local controller, sothat l the local controller will remain in synchronisrn by reaching itsresynchronization point normally slightly before the master cam MCRreaches its resynchronization point, and the local controller will thusrest momentarily each cycle for the resynchronization pulse from themaster controller. In order to assure that the master control cycle willapproximate the local controlcycle however, although being slightlylonger, over the entire range of the variable frequency power which maybe of the order of cycles to 120 cycles for example, the cam MC Y in themaster controller is set to open its contacts MSC-MSV and close itscontacts MSC-MSK for a period of time approximating the total of the twoyellow signal periods normally provided at the several local signalcontrollers, this period being ordinarily of the order of a total of 6or 7 seconds for example, thus operating the master cycle motor MSMthrough a small part of its cycle on fixed frequency and through theremainder of its cycle on the same variable frequency power supplied tothe local control motors.

Referring now to Fig. 3 another embodiment of the invention isillustrated schematically in which relays RAG and REG are provided,controlled by the respective green signal circuits to control theconnection of the coil LM2-LM3 of the local synchronous motor LSM to theoutput of the local amplifier LA or to the fixed frequency local power.In Fig. 3 the local amplifier LA and the local synchronous motor LSM,the local resynchronization relay LRS and the local rotary dials LDR andLDl and their associated contacts are the same as inFig. 2 but with therotary dials and associated contacts and the relay LSR slightlyrearranged in position for convenience of illustration of thestep-by-step ratchet drive for. the cams of the drum controller foroperating the it is assumed that the upper orinput side of the localamplifier LA is connected to the variable frequency power line VFL andVFR as in Fig. 2 and that the coil of the relay LRS is similarlyconnected by leads shown in part in Fig. 3, to the resynchronizationlines RSL and RSR as shown in Fig. 2.

In Fig. 3 the cams CAG, CAY, CBG and CBY are indicated schematically forthe control of the respective signal contacts and signals AG, AY, BG,and BY, these cams being indicated by the horizontal Broken line asrotated by the ratchet wheel DWR, which -'in aim is rotated by the livepawl Ll under control of the solenoid DS, the dead pawl FP serving toprevent reverse rotation of the ratchet wheel and cam shaft. Thesolenoid DS is controlled by the wire 20 and rotary dial switch contactLDSl corresponding to those shown in Fig. 2, the solenoid DS beingenergized momentarily and then deenergized as each 'pin 'DP engages thecontacts LDSl and passes by the contact. At each momentary energizationand deenergizatio-n of solenoid DS for example the live pawl LP ispulled away from and reengages the ratchet wheel DRW, the return strokeby spring action moving the ratchet wheel one tooth or one step and thusrotating the cainsas shown.

Cams controlling the red signals AR and BR are not shown in Fig. 3 forsimplicity of illustration, but it will be appreciated that the camcontrolling the red signal BR would have periods overlapping the periodsof cams CAG and CAY and close an associated pair of contacts for thesignal BR throughout the periods of the signal AG and the followingsignal AY, and the cam for the signal AR would also correspondingly havea period overlapping the periods of the cams CBG and CAY to close anassociated set of contacts throughout the periods of the signals BG andBY.

It will be noted in Fig. 3 that the relay RAG has an associated movablecontact RAG3 and fixed contacts RAG4- and RAGS. Relay RBG has associatedmovable contacts RBG3 and RBG6 with an associated normally open contactRBG3 and a normally closed contact RBG7. As indicated from the positionof the rotary dial H31 and the respective cams the cam shaftof the drumcontroller in Fig. 3 is illustrated in the A green signal period, inwhich the signal AG is operated, along with the signal BR (not shown inFig. 3). Consequen tly the relay RAG is shown energized and the relayRBG shown deenergizedin Fig. 3. Thus the normally closed contactsRAG3-RAG5 are shown open and the normally open contacts RAG3'-RAG4 areshown closed in Fig. 3. The relay RBG is shown in its normal deenergizedposition. The coil of the relay RAG is operated from the line LAGenergized from the now closed contact SAG connecting positive power tothis line, the other side of the relay being connected to the returnside of the power line or ground. The other cam controlled contactsillustrated for the signals AY, BG, and BY are shown open in thecondition of operation of the signal AG assumed and illustrated.

Considering the control of the motor circuit by the contacts of therelays RAG and RBG in more detail it will be observed that in theembodiment of the invention in Fig. 3, the contact arrangement issomewhat different from that of Fig. 2, thus illustrating anotherpossible circuit arrangement. output of the local amplifier LA at line35 is connected via either the contacts LDSS-LDS l or the contactsLRS3-LRS4 as previously described in connection with theresynchronization, and via wire 3'7 directly to one: terminal LM2 of themotor coil of the motor LSM. The control of the motor by relays RAG, RBGis entire ly on the other side LMS of the motor coil. Thus terminal LM3of the motor coil is connected via wire 38 and the now closed contactRAGS-RAG4 and wire as to the other side of the input of the amplifierLA. In the circuit as shown it is assumed that during the A green signalperiod the motor LSM is connected to be operated by the output of theamplifier LA, which is. the variable frequency power output.

If it is now assumed in connection with Fig. 3 that: the localcontroller has rotated to the B green signal position the cams will berotated so that the contact SAG will be open and relay RAG deenergizedand the contact SBG will be closedand the relay RBG consequentlyenergized along with the signal BG (and the In Fig. 3 one side ofthesignal AR not shown in Fig. 3). It will be noted that the signals AYand BY will not be energized by their associated cams and cam operatedcontacts in this now assumed condition of BG signal period. Thus with relay RAG deenergized and relay RBG energized the motor coil terminal LM3will be connected via wire 38 and the now closed contact RBG3-RBG4 tothe wire 36 and the output of amplifier LA. It will be observed thatalthough with the deenergization of relay RAG the contacts RAG3-RAG5will be closed the contacts RBG6RBG7 will also be open so that thepositive power of contact RBG7 is not connected to the motor coil LM atthis time.

If it is now assumed that the controller has rotated to either one ofthe two yellow signal positions then neither of the green signalcircuits will be operated by their associated cams and both relays RAGand RBG will consequently be deenergized. Under these conditions it willbe observed that the motor coil terminal LM3 is connected via wire 38the now closed contacts RAG3RAG5 and the now closed contacts RBG6 RBG7to the positive terminal of the local fixed frequency power supply, thecircuits via the other relay contacts and amplifier LA now being open.The left side of the output of amplifier LA is connected to the negativeterminal of the local fixed frequency power, which is thus applied tomotor coil terminal LM2 via wires 35, 37 and the resynchron-izingcontacts. Thus in either of the yellow signal positions of the localsignal controller the fixed frequency power supply will be connected tothe motor circuit.

The rotary dial and ratchet drive assembly along with theresynchronization relay LRS are shown enclosed in a broken line blockdesignated DD in Fig. 3, the motor LSM comprising its rotary element LMand the operating coil LM2LM3 being shown as outside of this block forconvenience of illustration, the block DD be ing repeated in outlineform only in the remaining Figs. 4, 5, and 6. in these remaining figuresit will be understood that the internal components of the block DD maybe as illustrated in Fig. 3 which can be conveniently referred to on thesame sheet of drawings.

Referring now to Fig. 4 only one of the cams of the drum controller isshown in this figure as reference may readily be had to the signal camsand associated contacts and circuits for the signals AG, AY, BG, and BYin Fig. 3. Fig. 4 shows another embodiment of the invention in which themotor circuit of the motor LSM is controlled by a relay RY operated incommon in the respective two yellow signal periods. In the embodiment ofthe invention an additional cam CY is provided on the drum controllerwith an associated cam operated switch which is closed in both of theyellow signal periods but open in the remaining signal periods of thecycle. The contacts SCY when closed connect positive power to the coilof the relay RY, the other side of this coil being connected to thenegative or grounded side of the power line. It is assumed that in Fig.4 the drum controller cam shaft is in the A green signal position and asillustrated therefore the contacts SCY are open and the relay RYdeenergized so that its normally closed contacts RY3-RY5 are shownclosed and its contacts RY3-RY4 are open. In this position, which isalso representative of the B green position of the cycle, the motor coilat terminal LM3 is connected via wire 48, RY3-RY5 and wire 46 to theoutput of the local ampli fier LA, the other side of the output of thelocal amplifier being connected to the other side of motor LM2 via thewire 35, DD and wire 37, as illustrated in Fig. 3.

It will be appreciated in Fig. 4 that if the controller is in either ofthe yellow periods of its cycle however the cam CY would be turned so asto close the contacts SCY and consequently energize the relay RY. Thiswill interrupt the circuit from amplifier LA to the motor coil by theopening of contacts RY3-RY5 and will close 12 the fixed frequency powersupply circuit to the motor coil via the contact RY3-RY4 and wire 48 aswill be obvious from the drawing.

Referring now to Fig. 5 another embodiment of the invention isillustrated showing the use of a relay RG common to both of the greensignal periods to control the operation of the motor circuit of motorLSM, the latter motor circuit being connected to the output of theamplifier LA during the green periods connected to the 10- cal fixedfrequency power supply during the remainder of the cycle, that is duringthe yellow signal periods. In Fig. 5 the cam CG is shown in one of thegreen signal periods with its associated contacts SCG closed to energizethe coil of the relay RG. Thus normally closed contacts RG3RG5 are shownopen in Fig. 5 and the normally open contacts RG3RG4 are shown closed.Thus during the green signal periods the output of the amplifier LA isconnected via wire 56 and the closed contacts RG4RG3 to the wire 58 andthe motor coil terminal LM3, the other side of the motor coil LM2 beingconnected via wire 37 and the block DD and wire 35 to the opposite sideof the output of the amplifier LA.

It will be obvious in Fig. 5 that during both of the yellow signalperiods the contact SCG will be open as the cam CG is turned for theseperiods and the relay RG will consequently be deenergized so that themotor coil will be disconnected at the open contact RG3-RG4 from theoutput of the amplifier LA and will be connected via the closed contactof RG3RG5 to the positive terminal of the local fixed frequency powersupply.

Fig. 6 illustrates still another embodiment of the invention in whichthe connections between the motor coil and the local amplifier or thelocal fixed frequency power supply are controlled directly by camoperated contacts in the local controller. In Fig. 6 the cams CY and CGare illustrated as operated by the rotary dial and ratchet assembly DDwith the contact SCY associated with CY open and the contact SCGassociated with CG closed, illustrating the position of the localcontroller in one of the green signal periods. Thus in the positionillustrated as shown in Fig. 6 the motor coil terminal LM3 is connectedvia wire 68 and closed contact SCG and wire 66 to the output of thelocal amplifier, the other side of the motor coil being connecteddirectly to the amplifier via DD as described above in connection withFig. 3. At this time the motor coil is disconnected from the local powersupply by the open contact SCY. It will be observed however that as thecams CY and CG rotate to either of the two yellow positions the contactSCG will be opened and the contact SCY will be closed in both of theyellow positions so as to open the connection between the motor and thelocal amplifier and close the circuit from the motor direct to thepositive terminal of the local fixed frequency power supply.

It will be appreciated that in Figs. 3, 4, 5 and 6 the lefthand side ofthe output of the amplifier is connected at all times to the negativeterminal of the local power in the form of the circuits illustrated inthese figures, for providing a return circuit for the fixed frequencypower connection. However, it will be appreciated that the connectionbetween this side of the local amplifier output and the terminal LM2 ofthe motor may also be interrupted and separated from the local powersupply and negative terminal by additional relay or cam operatedcontacts, along the lines of the interruption of both sides of the motorcircuit as illustrated in Fig. 2, in which case the connection of wire35 to negative power is unnecessary.

It will also be appreciated that the two contacts SCY and SCG could becombined into a single set of con tacts with the outer contact SCYcombined with the inner contact of SCG and connected to wire 68 as shownin Fig. 6, the outer contacts remaining connected as shown in Fig. 6 butthe combined inner contact being operated by cam CY to switch the motorterminal LM3 and wire 68 between wire 66 and positive power of fixedfrequency in lieu of the separate contacts and the associated cams CYand CG as shown in Fig. 6. Thus this alternative arrangement wouldcomprise the substitution of a single pole double throw switch for thetwo alternately operated single pole single throw switches SCY and SCGof Fig. 6. Another way of considering this alternative arrangement wouldbe the direct operation of the movable contact RY3 to control itsassociated contacts KY4 and KY5 of Fig. 4 directly by the cam CY insteadof through the intermediate relay RY and contacts SGY.

It will be understood that the drum unit DD may be resynchronizedcyclically with therotary dial unit LD1 LDR by means of cooperatingadditional drum and dial pin control contacts as is well known in theart.

For simplicity of illustration in Figs. 2 and 3 for example the normaldrum advance contacts LDSil and the resynchronization contacts LDS2i-4are shown operated by separate rotary dials LDl and LDR respectivelyrotatedin synchronism by the synchronous motor LSM. it will beunderstood however that these two rotary dial units may be combined.into one rotary dial unit, if desired, with the pin RP longer than thepins DP and with the dial contacts arranged so that LDSl is operated bythe pins DP only and LDS3 is operated by the pin RP only, as is commonpractice in well known types of rotary dial traffic signal controllers.

It will be appreciated that the green signal display period may overlapthe yellow signal display period in some traflic control systems byoverlapping cam arrangements as is well known .in the art, but the greenand yellow overlap period then would be considered the clearance periodand the green alone would be considered the go or true green period.

It will beappreciated also by those skilled in the art that theswitching between variable frequency and fixed frequency power inaccordance with the invention may be on the input side of the amplifierLA or MA for example instead of on the .output side as shown in theseveral figures of the drawings but with similar circuits and with avoltage matching transformer interposed where the voltage of thevariable frequency power is different from that of the fixed frequencypower.

It will be understood that the frequency of the variable frequency poweras the term is used herein is variable in the sense that it may .beadjusted as desired for remote control of the green signal parts of thecycle or total cycle for example but such frequency may remain at somedesired constant value for a considerable period of time, such as forone or several signal cycles for example and may then be changed toanother constant value for a further period of time, but the frequencyof the variable frequency power may also be changed if desired at anytime during the cycle.

As previously pointed out the master cycle unit preferably has aslightly longer time cycle than the local rotary dial cycle controlunits for cyclic resynchronization. This may be accomplished by theemployment of a slightly larger gear reduction for the master cycle unitthan for the local dial units, where these units are drivenconventionally by the respective synchronous motors through gearing, forexample. As an alternative arrangement however, it will be appreciatedthat the fixed frequency supply of the master control unit MCU connectedby MSK may have a lower frequency than the local fixed frequency toinsure a slightly longer master cycle.

Although a number of alternate forms or arrangements of apparatusaccording to the invention have been pointed out above, it will beobvious to those skilled in the art that other modifications of theapparatus or of the arrangement or character of its parts may be madewithout departing from the spirit of the invention within the scope ofthe claims.

I claim:

1. A trafiic control system for interfering trafiic lanes includingright-of-way signals for the respective lanes, clearance signals for therespective lanes, cyclicswitch means for operating the respectiveright-of-way signals in succession and for operating the respectiveclearance signals between the respective successive right-of-way signaloperations, synchronous motor drive means for operating said cyclicswitch means through its cycle, a remotely controlled variable frequencycircuit means for operating said synchronous motor at varying speeds inaccordance with varying frequency on said circuit means when connected,a fixed frequency circuit means, and further switch means cooperatingwith said cyclic switch means for connecting said variable frequencycircuit means to operate said synchronous motor driving means during theright-of-way signal operating parts of such cycle and for connectingsaid fixed frequency circuit means to operate said synchronous motorduring the clearance signal operating parts of such cycle.

2. A trafi'ic signal controller including two sets of signal circuitsfor go signals and clearance signals for two interfering traflic lanes,a cyclic switch unit having a cycle of operation for the go andclearance signal circuits for one set followed by the go and clearancesignal circuits for the other set of signals, a frequency responsivedriving means for said cyclic switch for operating the latter atvariable time rates in response to variations in frequency, a variablefrequency source for said driving means, a fixed frequency source forsaid driving means, and switch means controlled by said cyclic switchfor operatively connecting said driving means to said variable frequencysource during a part of its cycle and to the fixed frequency sourceduring another part of its cycle.

3. Atraific signal controller including two sets of signal circuits forgo signals and clearance signals for two interfering traffic lanes, acyclic switch unit having a cycle of operation forthe go and clearancesignal circuits for one set followed by the go and clearance signalcircuits for the other set, when operating, a frequency responsivedriving means for said cyclic switch for operating the latter atvariable time rates in response to variations in frequency, a variablefrequency source for said driving means, a fixed frequency source forsaid driving means, and switch means controlled by said cyclic switchmeans for operatively connecting said driving means to said variablefrequency source during the go signal parts of the cycle and to saidfixed frequency source during the clearance signal parts of the cycle.

4. in .a traffic signal control system, a. signal circuit controllerhaving a cycle of operation, a frequency re sponsive driving meansincluding a syncl'ironons motor for operating said controller atvariable speed in accordance with variable frequency, a variablefrequency alternating current power circuit, a fixed frequencyalternating current power source, and switch means operated by saidcontroller in its cycle to operatively connect said variable frequencypower circuit to said synchronous motor driving means during a part ofthe cycle and to connect said fixed frequency power source to saiddriving means during another part of the cycle and remote control meansfor varying the frequency of said variable frequency circuit.

5. in a traffic signal control system, a signal circuit controllerhaving a cycle of operation, a frequency responsive driving means foroperating said controller at variable time rates in accordance withvariable frequency, a variable frequency power circuit, a fixedfrequency power source, switch means operated by said controller in itscycle to operatively connect said variable frequency power circuit tosaid driving means during a part of the cycle and to connect said fixedfrequency power source to said driving means during another part of thecycle, and remote control means for varying the frequency of saidvariable frequency power circuit.

6. In a traffic control system, a fixed frequency power supply, avariable frequency power supply, a traflic signal controller having acycle of positions through which it is adapted to be operated forcontrol of a traffic signal at variable time rates in accordance withvariable frequency input to the controller; said cycle including aposition for operating a first go signal, a following position foroperating a first clearance signal, a following position for operating asecond go signal and a following position for operating a secondclearance signal, and means controlled by said controller in its cycleof operation to connect said variable frequency power supply as input tosaid controller during the go signal operating positions of said cycleand to connect said fixed frequency power supply as input to saidcontroller during the clearance signal operating positions of saidcycle.

7. In a tratfic control. system, a master control unit having a variablefrequency power generator, means for varying the frequency output ofsaid generator, a fixed frequency power source, a cyclic controlleroperable at variable time rates through its cycle in accordance withvariations of 'requency applied to operate it, and switch meanscontrolled by said cyclic controller in its cycle to apply the variablefrequency output of said generator to operate said controller during amajor part of its cycle and to apply said fixed frequency power fromsaid power source to operate said controller through a minor part of itscycle; a local signal controller having a cycle of operation for trafficsignal control, a frequency responsive driving means for said localcontroller, and switch means operated by said local controller in itscycle to operativcly connect the variable frequency power from saidmaster control unit to said driving means during the major part of saidlast named cycle and to operatively connect a corresponding fixedfrequency source to said driving means during a corresponding minor partof said last named cycle, and means for cyclically resynchronizing thelocal controller cycle with the master controller cycle.

8. In a trafic control system, a master control unit having a variablefrequency power generator, means for varying the frequency output ofsaid generator, a fixed frequency power source, a cyclic controlleroperable at variable time rates through its cycle in accordance withvariations of frequency applied to operate it, and switch meanscontrolled by said cyclic controller in its cycle to apply the variablefrequency output of said generator to operate said controller during themajor part of its cycle and to apply said fixed frequency power fromsaid power source to operate said controller through a minor part of itscycle; a local signal controller having a cycle of operation for trafficsignal control, a frequency responsive driving means for said localcontroller, and switch means operated by said local controller in itscycle to operatively connect the variable frequency power from saidmaster control unit to said driving means during the major part of saidlast named cycle and to operatively connect a corresponding fixedfrequency source to said driving means during a corresponding minor partof said last named cycle, said local controller being operated by itsfrequency responsive driving means through its cycle in a slightlyshorter time than said master cyclic controller and means controlledcooperatively by said master controller and said local controller forcyclically resynchronizing the local controller cycle with the mastercontroller cycle by causing the local controller to dwell in part ofeach cycle until the master controller reaches the corresponding pointin. its cycle.

9. in a trafiic control system of the master-local type, a mastercontrol unit having a variable frequency power generator, means forvarying the frequency output of said generator, 21 fixed frequency powersource, a cyclic controller operable at variable time rates through itscycle in accordance with variations of frequency applied to operate it,and switch means controlled by said cyclic controller in its cycle toapply the variable frequency output of said generator to operate saidcontroller dur ing a major part of its cycle and to apply the fixedfrequency power from said power source to operate said controllerthrough a minor part of its cycle; a local signal controller having acycle of operation for traffic signal control including a phase fortraffic right-of-way followed by traffic clearance and a second phasefor other traffic right-of-way followed by other traffic clearance, afrequency responsive driving means for said local controller, and switchmeans operated by said local controller in its cycle to connect thevariable frequency power from said master control unit to said drivingmeans during the said right-of-way parts of said last named cycle and toconnect a fixed frequency source corresponding to the first mentionedfixed frequency source to said driving means during the trafficclearance parts of said last named cycle, said major part of the firstnamed cyclic controller cycle corresponding with the right-of-way partsof the local controller cycle and the minor part of the first namedcyclic controller cycle corresponding with the traflic clearance partsof the local controller cycle, means including other switch meanscontrolled by the first named cyclic controller in the master controlunit and further switch means operated by said local con troller in thecycle of the latter and interconnecting circuit means cooperating tointerrupt temporarily the operation of the local controller once percycle until the master controller arrives at a correspondingpredetermined point in the master control cycle for cyclicallyresynchronizing the local controller cycle with the master controllercycle.

10. A traffic signal controller including output circuits for a first gosignal, a first clearance signal, a second go signal and a secondclearance signal, a cyclic switch unit having a cycle of operation forthe several signal circuits in sequence respectively when operating, afrequency responsive driving means for operating said cyclic switch unitat variable time rates in response to variations in frequencyrespectively, a variable frequency input circuit for said driving means,a fixed frequency input circuit for said driving means, and relay meansoperated by said clearance signal circuits to connect said fixedfrequency circuit to said driving means during operation of saidclearance signal circuits and to connect said variable frequency circuitto said driving means during operation of said go signal circuits duringsaid cycle of operation.

11. A traffic signal controller including output circuits for a first gosignal, a first clearance signal, a second go signal and a secondclearance signal, a cyclic switch unit having a cycle of operation forthe several signal circuits in sequence respectively when operating, afrequency responsive driving means for operating said cyclic switch unitat variable time rates in response to variations in frequencyrespectively, a variable frequency input circuit for said driving means,a fixed frequency input circuit for said driving means, and relay meanscontrolled by said go signal circuits to connect said variable frequencycircuit to and disconnect said fixed frequency circuit from said drivingmeans during operation of said go signal circuits and to connect saidfixed frequency circuit to and disconnect said variable frequencycircuit from said driving means during operation of said clearancesignal circuits.

12. A traffic signal controller including output circuits for a first gosignal, a first clearance signal, a second go signal and a secondclearance signal, a cyclic switch unit having a cycle of operation forthe several signal circuits in sequence respectively when operating, afrequency responsive driving means for operating said cyclic switch unitat variable time rates in response to variations in frequencyrespectively, a variable frequency input circuit for said driving means,a fixed frequency input circuit for said driving means, switch meansoperated by said cyclic switch unit in both of the clearance signalcircuit operating periods only in said cycle, and relay means operatedby such operation of said switch means to connect said fixed frequencycircuit to and disconnect said variable frequency circuit from saiddriving means during said clearance periods and to connect said variablefrequency circuit to and disconnect said fixed frequency circuit fromsaid driving means during the remaining signal operating periods in saidcycle.

13. A traffic signal controller including output circuits for a first gosignal, a first clearance signal, a second go signal and a secondclearance signal, a cyclic switch unit having a cycle of operation forthe several signal circuits in sequence respectively when operating, afrequency responsive driving means for operating said cyclic switch unitat variable time rates in response to variations in frequencyrespectively, a variable frequency input circuit for said driving means,a fixed frequency input circuit for said driving means, switch meansoperated by said cyclic switch unit in both of the go signal circuitoperating periods only in said cycle, and relay means operated by suchoperation of said switch means to connect said variable frequencycircuit to and disconnect said fixed frequency circuit from said drivingmeans during said go periods and to connect said fixed frequency circuitto and disconnect said variable frequency circuit from said drivingmeans during the remaining clearance signal operating periods in saidcycle.

14. A trafiic signal controller including output circuits for a first gosignal, a first clearance signal, a second go signal and a secondclearance signal, a cycle switch unit having a cycle of operation forthe several signal circuits in sequence respectively when operating, afrequency responsive driving means for operating said cyclic switch unitat variable time rates in response to variations in frequencyrespectively, a variable frequency input circuit for said driving means,a fixed frequency input circuit for said driving means, switch meansoperated by said cyclic switch unit in both of the go signal circuitoperating periods only in said cycle for connecting said variablefrequency circuit to said driving means during said go periods only, andadditional switch means operated by said cyclic switch unit in both ofthe clearance signal periods only in said cycle to connect said fixedfrequency circuit to said driving means only in said clearance periods.

15. A trafiic signal controller including output circuitsfor a first gosignal, a first clearance signal, a second go signal and a secondclearance signal, a cyclic switch unit having a cycle of operation forthe several signal circuits in sequence respectively when operating, afrequency responsive driving means for operating said cyclic switch unitat variable time rates in response to variations in frequencyrespectively, a variable frequency input circuit for said driving means,a fixed frequency input circuit for said driving means, and relay meanscontrolled by said signal circuits to connect said fixed frequencycircuit to said driving means during operation of the respectiveclearance signal circuits and to connect said variable frequency circuitto said driving means during operation of the respective go signalcircuits.

16. In a trafiic control system, a first frequency source, a secondfrequency source, a signal circuit controller having a cycle ofoperating positions including a plurality of right-of-way signal circuitpositions and following clearance signal circuit positions, a rotarydial cycle distribution unit for operating said signal circuitcontroller through its cycle of positions and having actuating elementstherefor arranged in adjustable angular relationship for determining theproportions of its total cycle allocated to the respective right-of-wayperiods and respective clearance periods for any predetermined speed ofrotation of said rotary dial unit, a synchronous motor for driving saidrotary dial unit at a speed substantially proportional to the frequencyinput thereto, switch means controlled by said signal circuit controllerfor connecting said first frequency source to said synchronous motor insaid rightof-way signal positions and for connecting said secondfrequency source to said synchronous motor in said clearance positions,and remote controlmeans for varying the frequency of said firstfrequency source to vary the speed of said synchronous motor to vary thelength of the rightof-way periods while the relative proportions of therespective right-of-way signal periods to each other is maintained asdetermined by said relationship of said actuating elements on saidrotary dial unit and the length of the clearance periods isindependently maintained by said second frequency source and therelationship of the actuating elements of said rotary dial unit.

17. In a traffic control system of the master-local control type, afirst frequency supply circuit; a second frequency supply circuit; aplurality of local signal circuit controllers each having a cycle ofoperating positions including a plurality of right-of-way signal circuitpositions and following clearance circuit positions, a rotary dial cycledistribution unit having actuating elements arranged in adjustableangular relationship for operating said signal circuit controllerthrough its cycle of positions and determining the proportions of itstotal cycle allocated to the respective right-of-way periods andclearance periods for any predetermined speed of rotation of said rotarydial unit, a synchronous motor for driving said rotary dial unit at aspeed substantially proportional to the frequency input thereto,switching means controlled by said signal circuit controller forconnecting said firstfrequency supply circuit to said synchronous motorin said right-of-way signal positions and for connecting said secondfrequency supply circuit to said synchronous motor in said clearancepositions, and a further actuating element and associated switch meansin said rotary dial unit for interrupting the rotation thereof at anydesired part of its cycle of operation in desired relationship to one ofthe respective right-ofiway periods, all associated With and individualto each local signal circuit controller; a master controller includingmeans for varying the frequency of the first frequency supply circuit, amaster cyclic switch unit operable through its cycle at a speedsubstantially proportional to frequency input thereto and having switchmeans for connecting the input of the cyclic switch unit to a frequencysource of substantially the same frequency as said second frequencysupply circuit for a part of its cycle approximating the total time ofthe said clearance periods and for connecting the input of the cyclicswitch unit to said first frequency supply circuit during substantiallythe remainder of its cycle, and further switch means operated by saidcyclic switch unit in a predetermined part of the cycle of the latterfor restarting rotation of the several local rotary dial units insynchronism cyclically with the cyclic switch unit in the mastercontroller.

References Cited in the file of this patent UNITED STATES PATENTS

